You put in the time—and the sweat! So don't let these common misconceptions get you off track.

Can you really blast more fat by working out on an empty stomach? Do you burn the same number of calories walking a mile rather than running? We asked fitness pros to weigh in on five of the most common exercise myths and tell us the real deal—so you can get the best results out of each and every workout.

Myth: You burn more fat if you exercise on an empty stomach. Reality: Don't expect any fat-melting miracles. When you exercise, your body burns both fat and carbohydrate calories. Recent studies show that working out on an empty stomach might burn a few more fat calories than when you work out an hour or two after eating—but total calorie burn is about the same. And, based on research so far, that's what really counts when it comes to fitting into a smaller size. What scientists don't yet know is whether an increase in fat burn alone could help you lose weight faster or shed more pounds over time. So the choice about when to eat is yours. I've found I can do my 30- to 45-minute walks on an empty stomach no problem, but I need to fuel up before longer bike rides with my husband. To determine what's right for you, try this experiment: Eat a snack of about 200 calories—like a banana with peanut butter, whole grain crackers and low-fat cheese, or an energy bar—1 to 2 hours before you exercise, then note how you perform. How long can you go before you feel tired? Can you pick up the intensity? The next day, work out without eating and note any differences. Exercising on an empty stomach can backfire by decreasing your calorie burn if you're too tired to complete your workout or slack off during it. Source: Michele Stanten, a certified group fitness instructor and counselor in the areas of weight control and stress management

Myth: Walking at a leisurely pace for an hour is a good way to fit in exercise. Reality: Any activity is better than none but if you want to lose weight you probably have to ramp it up. While shorter amounts of slow walking (about 2.5 to 3 mph) can improve insulin sensitivity, increase energy, reduce stress, and lower blood pressure, if your goal is weight loss, the results will depend on your starting point. If you're very overweight or just beginning to be active, "leisurely" walking most days a week may be enough to help you lose a few pounds. But once your body adjusts to this level of activity, you'll need to step up the pace to continue to lose. Source: Cedric Bryant, PhD, chief science officer, American Council on Exercise

Myth: You burn the same number of calories whether you walk or run a mile. Reality: Lab studies show that running a mile can burn as much as 30% more calories than walking, depending on your speed. That's because running takes more effort, so you use more calorie-burning muscles throughout your entire body. (When you run, you lift your body weight off the ground with every step; when you walk, one foot is always grounded.) Source: Cedric Bryant, PhD, chief science officer, American Council on Exercise

Myth: You can turn fat into muscle. Reality: Fat and muscle are different tissues, and one cannot morph into the other. But sometimes it may seem like they do. That's because you start to lose muscle mass in your 30s, especially if you don't strength-train. This can slow metabolism by 3% per decade, enough to pack on up to 23 extra pounds. The fat usually shows up in the spots where you once had firm muscle, like the backs of your arms. Women tend to have more fat cells in these areas, and as the muscles shrink, those fat cells expand. That's why we recommend a two-part approach to get toned: Blast fat with cardio workouts and build muscle with strength-training.Source: Wayne L. Westcott, PhD, Prevention advisor; senior fitness research director, South Shore YMCA, Quincy, MA

Myth: Muscle "weighs" more than fat. Reality: A pound of muscle weighs the same as a pound of fat. But the body fat is more "fluffy" and the muscle is more dense and compact. Muscles take up less space in your body, so body weight may go up as you add compact, tight muscle mass. How do you measure your ratio of body fat to lean muscle mass? You could try a bioelectrical impedance scale—or a body fat scale. These are available at most sporting goods stores. When you stand on the scale, a safe, low-level electrical signal passes through your body. You can then compute the percentage of body fat based on the resistance the signal encounters as it travels through your body.There's also the body fat caliper. This is fairly accurate and easy to do. Your gym should be able to help you out. A personal trainer will use this caliper to take a few measurements. Through a formula and calculation, you can determine your body fat. Remember: Muscles need more calories a day, so the more muscles you have, the more calories you burn and the more weight loss you see! Source: Chris Freytag, author of 2-Week Total Body Turnaround